#include <linux/mktime.h>

/*
 * This isn't the library routine, it is only used in the kernel.
 * as such, we don't care about years<1970 etc, but assume everything
 * is ok. Similarly, TZ etc is happily ignored. We just do everything
 * as easily as possible. Let's find something public for the library
 * routines (although I think minix times is public).
 */
/*
 * PS. I hate whoever though up the year 1970 - couldn't they have gotten
 * a leap-year instead? I also hate Gregorius, pope or no. I'm grumpy.
 */
#define MINUTE 60
#define HOUR   (60 * MINUTE)
#define DAY    (24 * HOUR)
#define YEAR   (365 * DAY)

/* interestingly, we assume leap-years */
static int month[12] = {
    0,
    DAY * (31),
    DAY * (31 + 29),
    DAY * (31 + 29 + 31),
    DAY * (31 + 29 + 31 + 30),
    DAY * (31 + 29 + 31 + 30 + 31),
    DAY * (31 + 29 + 31 + 30 + 31 + 30),
    DAY * (31 + 29 + 31 + 30 + 31 + 30 + 31),
    DAY * (31 + 29 + 31 + 30 + 31 + 30 + 31 + 31),
    DAY * (31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30),
    DAY * (31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31),
    DAY * (31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30)};

long kernel_mktime(struct mktime *time) {
    long res;
    int year;

    year = time->year - 70;
    /* magic offsets (y+1) needed to get leapyears right.*/
    res = YEAR * year + DAY * ((year + 1) / 4);
    res += month[time->mon];
    /* and (y+2) here. If it wasn't a leap-year, we have to adjust */
    if (time->mon > 1 && ((year + 2) % 4))
        res -= DAY;
    res += DAY * (time->day - 1);
    res += HOUR * time->hour;
    res += MINUTE * time->min;
    res += time->sec;
    return res;
}
